A temperature-stable resistor is made by connecting a resistor made of silicon in series with one made of iron. If the required total resistance is 1300 Q in a wide temperature range around 20°C, what should be the resistance of the (a) silicon resistor and (b) iron resistor? (See the table below.) Resistivities of Some Materials at Room Temperature (20°C) Resistivity, p (N m) Temperature Coefficient of Resistivity, a (K-) Material Typical Metals Silver 1.62 x 10-8 4.1 x 10- Copper Gold Aluminum 1.69 x 10-8 4.3 x 10-3 2.35 x 10 4.0 x 10- 2,75 x 10-8 4.4 x 10- Manganin Tungsten Iron 4.82 x 10 8 0.002 x 10- 4.5 x 10- 5.25 x 10- 9.68 x 10-8 6.5 x 10- 3,9 x 10 Platinum 10.6 X 10* Typical Semiconductors 2.5 x 10 Silicon, pure -70 x 10-3 Silicon, n-type" Silicon, p-type 8.7 x 104 2.8 x 10- Typical Insulators 101 104 Glass Fused quartz ~10% "An alloy specifically designed to have a small value of a. "Pure silicon doped with phosphorus impurities to a charge carrier density of 10" m Pure silcon doped with aluminum impurities to a charge carrier density of 10" m. (a) Number i Units (b) Number Units

A heating element is made by maintaining a potential difference of 89.0 V across the length of a Nichrome wire that has a 4.96 x 10-6 m2 cross section. Nichrome has a resistivity of 5.00 x 10-7 2:m. (a) If the element dissipates 2880 W, what is its length? (b) If 102 V is used to obtain the same dissipation rate, what should the length be? (a) Number Units (b) Number Units

(a) A 35.1-m length of copper wire at 20.0°C has a radius of 0.23 mm. If a potential difference of 7.0 V is applied across the length of the wire, determine the current in the wire. (Use the values in the following table.) Resistivities and Temperature Coefficients of Resistivity for Various Materials (at 20°C) Material Resistivity(Ω · m) Temperature Coefficientof Resistivity [(°C)−1] Silver 1.59 ✕ 10−8 3.8 ✕ 10−3 Copper 1.7 ✕ 10−8 3.9 ✕ 10−3 Gold 2.44 ✕ 10−8 3.4 ✕ 10−3 Aluminum 2.82 ✕ 10−8 3.9 ✕ 10−3 Tungsten 5.6 ✕ 10−8 4.5 ✕ 10−3 Iron 10.0 ✕ 10−8 5.0 ✕ 10−3 Platinum 11 ✕ 10−8 3.92 ✕ 10−3 Lead 22 ✕ 10−8 3.9 ✕ 10−3 Nichromea 150 ✕ 10−8 0.4 ✕ 10−3 Carbon 3.5 ✕ 10−5 −0.5 ✕ 10−3 Germanium 0.46 −48 ✕ 10−3 Silicon 640 −75 ✕ 10−3 Glass 1010–1014   Hard rubber ≈1013   Sulfur 1015   Quartz (fused) 75 ✕ 1016   aA nickel–chromium alloy commonly used in heating elements.  Calculate the resistance of the wire and use the value you calculate to find the current…

A ceramic resistor of unknown resistance has a cross-sectional area of 0.753 cm2 and a length of 2.43 cm. A current of 0.926 mA results when a 15.00 V is dropped across it. The resistivity of the ceramic is